"Speaker Martin is not the right man to have at the helm," he told the BBC. "He is too compromised."

"It is a question of competence and acting fairly and in a non-partisan manner," he said.

Mr Carswell, a long-time critic of Mr Martin, says he has already picked up more than half a dozen sponsors for his motion and that it has cross-party support.

But he told the BBC he wanted to give MPs the opportunity to go back to their constituencies at the weekend, to understand the public anger about the expenses furore and realise change is needed.

"We need a new speaker with a mandate for radical change to make politicians work for the people," he said.

"I'm not having a dig at Michael Martin because he is anything other than a decent, honest, honourable man.

"I just happen to think he is bad at doing the job of Speaker."

'Pearls of wisdom'

Newport West MP Paul Flynn told BBC Wales: "He hasn't led the House of Commons - he's been too defensive and has actually attacked the whistleblowers. We need someone who is interested in exposing the errors of the past and is willing to introduce new rules."

And Liberal Democrat frontbencher Norman Lamb told the BBC he would sign the motion.

"The final straw came on Monday when he attacked backbenchers in Parliament over this whole expenses debacle. And I felt that at that point he lost his impartiality," Mr Lamb said.

The BBC's political editor Nick Robinson said the number of public calls for Mr Martin to go was unprecedented.

On Monday, in a statement to the Commons, Mr Martin angrily defended the decision to ask police to investigate where the expenses leak came from.

He rebuked Labour MP Kate Hoey, who said it was a waste of money when police had a "huge" job to do in London, telling her: "I hear your public utterances and your pearls of wisdom on Sky News. It's easy to talk then."

He also rebuked Lib Dem MP Norman Baker, who has long campaigned for greater transparency on MPs' expenses, as "another member who is keen to say to the press what the press wants to hear".

Mr Baker said later he "appeared to be defending vested interests rather than leading us out of this mess".

In further bad-tempered exchanges on Tuesday Labour's David Winnick challenged Mr Martin to apologise for his comments to Ms Hoey.

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